The present invention relates to electronic equipment having optical communication function and a CPU which can take a standby mode and, more particularly, to such electronic equipment using batteries or the like.
Conventionally, as seen in Japanese Patent Laid-Open Publication HEI 5-193427, in electronic equipment having a standby mode function and enabled to execute optical communication, the power for the optical communication part is kept interrupted in the standby mode so that the power consumption of the equipment is lowered.
In this prior art, there have been issues including:
1) In the standby mode of the equipment, because the power for the optical communication part is kept interrupted, the cancellation of the standby mode with an optical signal is impossible; and PA1 2) Although the above issue can be solved by not interrupting the power for the optical communication part, a) power consumption of the optical communication part increases. b) Because optical communication is not enabled unless the standby mode is canceled, it cannot be discriminated whether input light is noise or a signal. As a result, the standby mode would be canceled even with optical noise such as extraneous light, causing the power consumption to increase. PA1 Even in the standby mode of the electronic equipment on the reception side, optical communication is enabled by canceling the standby mode with an optical input by using the sub-clock; and PA1 Because this advantageous result is enabled without increasing the power consumption, service life of the battery such as cells can be prolonged. PA1 In the standby mode of the electronic equipment on the reception side, it can be discriminated whether the received input is optical noise such as extraneous light or a signal. Therefore, the standby mode can be canceled only with an optical input, so that unnecessary standby cancellations can be eliminated; and PA1 Because this advantage is accomplished without using the main clock, there is no need of complex operations (programs) of the CPU so that the load on the CPU is reduced.
Therefore, an object of the present invention is to provide a circuit which can execute optical communication by implementing the standby cancellation with an optical signal when necessary and correctly, without increasing the power consumption (without the standby mode being unnecessarily canceled by extraneous optical noise).
In order to achieve the above object, there is provided Electronic equipment having a transmission/reception circuit for optical communication, and a CPU which is operated by programs and can be switched to either an operation mode or a standby mode involving less power consumption than the operation mode, the electronic equipment comprising: measuring instrument for, in the standby mode of the CPU, measuring frequency of light inputted from the transmission/reception circuit by using a clock which is operating in the standby mode, and frequency discriminating instrument for discriminating whether or not the measured frequency is a desired frequency, wherein the CPU is changed from the standby mode to the operation mode depending on a discrimination result of the frequency discriminating instrument, and optical communication is executed by the transmission/reception circuit.
According to the above construction, in electronic equipment having a standby function and optical communication, the power for the optical communication part is turned ON/OFF by referencing the sub-clock in the standby mode. Then, over the measurement of an inputted optical signal, when the optical signal is a desired frequency, the standby mode is canceled so that the optical communication is enabled. As a result, there are produced advantages that:
In an embodiment of the present invention, a reception side has a signal feedback circuit for, based on a discrimination result of the frequency discriminating instrument, feeding back the discrimination result to a transmission side, and the transmission side outputs a signal with a frequency different from the frequency of the received signal, and this sequence is iterated a plurality of times.
According to the above construction, in electronic equipment having a standby function and optical communication, the power for the optical communication part is turned ON/OFF by referencing the sub-clock in the standby mode. Then, over the measurement of an input optical signal, when the signal is a desired frequency, the discrimination result is fed back to the transmission side, so that the frequency of the optical signal from the transmission side is changed, and similar sequence is iterated.
By this operation, it is discriminated whether the optical input is extraneous noise or a desired signal. After the discrimination, the standby mode is canceled. As a result, there are produced advantages that: